Vertebral defect device

ABSTRACT

A vertebral defect device includes a housing having a convexly tapered distal end, a convexly tapered proximal end, a top, a bottom, an anterior side, a posterior side and an outer surface having generally rounded edges thereby facilitating insertion into an intervertebral space between a pair of adjacent vertebrae. The length of the housing as measured from the distal end to the proximal end is greater than the width of the housing as measured between the anterior and posterior sides and is greater than the height of the housing as measured between the top and bottom.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of co-pending U.S. patentapplication Ser. No. 10/988,830 filed Nov. 15, 2004, entitled “Methodsof Installing a Vertebral Defect Device,” which is a divisional of U.S.patent application Ser. No. 10/345,591, filed Jan. 16, 2003 entitled“Vertebral Defect Device.” This application claims benefit of U.S.Provisional Patent Application No. 60/369,510 filed Apr. 2, 2002,entitled “Intervetebral Fusion Cage” and U.S. Provisional PatentApplication No. 60/349,730 filed Jan. 17, 2002, entitled “IntervetebralFusion Cage.”

BACKGROUND OF THE INVENTION

The present invention relates generally to intervertebral defectdevices, and more particularly, to an intervertebral defect device forinsertion into an intervertebral space using minimally invasivetechniques.

Referring to prior art FIGS. 9 and 10, the spine 120, also known as thevertebral column or the spinal column, is a flexible column of vertebrae100 (special types of bones) held together by muscles, ligaments andtendons. The spine 120 extends from the cranium (not shown) to thecoccyx 126, encasing a spinal cord 128 and forming the supporting axisof the body (not shown). The spinal cord 128 is a thick bundle of nervetissue (nerves) that branch off to various areas of the body for thepurposes of motor control, sensation, and the like. The spine 120includes seven cervical vertebrae (not shown), twelve thoracic vertebrae(not shown), five lumbar vertebrae, L^(I)-L^(V), five sacral vertebrae,S^(I)-S^(V), and three coccyx vertebrae 126. The sacral and coccyxvertebrae are each fused, thereby functioning as a single unit. FIG. 10shows the lumbar region 122, the sacral region 124 and the coccyx 126 ofthe spine 120 and that the vertebrae 100 are stacked one upon another.The top portion 100 a and bottom portion 100 b of each vertebrae 100 isslightly concave. The opposing concave vertebral surfaces form theintervertebral space 121 in which an intervertebral disk (not shown)resides. Each of the intervertebral disks has a soft core referred to asa nucleus pulposus or nucleus (not shown).

In FIG. 9, directional arrow 101 a is pointing in the posteriordirection and directional arrow 101 b is pointing in the anteriordirection. FIG. 9 shows that each vertebrae 100 includes a body 106 inthe innermost portion, a spinal canal 108 and a spinous process 102 atthe posterior-most end of the vertebra 100. The vertebrae 100 aresubstantially similar in composition, but vary in size from the largerlumbar vertebrae to the smallest coccyx vertebrae 126. Each vertebrae100 further includes two transverse processes 104 located on either sideand a protective plate-like structure referred to as a lamina 110.Nerves from the spinal cord 128 pass through the spinal canal 108 andforamina 111 to reach their respective destinations within the body.

The natural aging process can cause a deterioration of theintervertebral disks, and therefore, their intrinsic support strengthand stability is diminished. Sudden movements may cause a disk torupture or herniate. A herniation of the disk is primarily a problemwhen the nucleus pulposus protrudes or ruptures into the spinal canal108 placing pressure on nerves which in turn causes spasms, tingling,numbness, and/or pain in one or more parts of the body, depending on thenerves involved. Further deterioration of the disk can cause the damageddisk to lose height and as bone spurs develop on the vertebrae 100,result in a narrowing of the spinal canal 108 and foramen 111 (not shownclearly), and thereby causes pressure on the nerves emanating from thespinal cord 128.

Presently, there are several techniques, in addition to non-surgicaltreatments, for relieving the symptoms related to intervertebral diskdeterioration. Surgical options include chemonucleolysis, laminectomy,diskectomy, microdiskectomy, and spinal fusion.

Chemonucleolysis is the injection of an enzyme, such as chymopapain,into the disk to dissolve the protruding nucleus pulposus. The enzyme isa protein-digesting enzyme and is used to dissolve the disk material.Since the enzyme is essentially a tissue-dissolving agent, it isindiscriminate in the protein-based matter it dissolves. Should theenzyme be injected into the wrong place, or if there is a breach in thedisk capsule that would allow the solution to enter the spinal canal orto contact nerve tissue or the like, the resultant damage to nervetissue could not be reversed. Even worse, about half of the patients whoreceive chemonucleolysis treatments experience increased back pain andmuscle spasms immediately after the injection and more than half haveincapacitating back pain for durations up to three months after suchtreatments.

A laminectomy is performed to decompress the spinal canal by opensurgical techniques under general anesthesia. In this procedure, thelamina 110, (the bone that curves around and covers the spinal canal 108as shown in FIG. 9), and any disk tissue causing pressure on a nerve orthe spinal canal 108, are partially removed. This technique is highlyinvasive and traumatic to the body, and therefore requires an extendedrecovery time of about five weeks and a hospital stay of a few days. Inaddition to the trauma inflicted on the body from even a successfulsurgery, there are increased risks of future problems due to the removedportion of the lamina 110 which is no longer in place to support andprotect the spinal canal 108 at the area where the surgery took place.

Further, the vertebrae 100 may shift due to the lack of support in thestructure. Thus, simply removing the disk and parts of the vertebralbone is a short-term, pain-relieving corrective action but not along-term solution.

Diskectomy is a form of spinal surgery wherein part of an intervertebraldisk is excised typically through open surgical techniques. Recently,less invasive techniques referred to as percutaneous diskectomy ormicrodiskectomy have been developed to reduce the surgical trauma to thepatient. In microdiskectomy, a much smaller incision is made than innormal open surgeries. A small retractor, working channel or tube isinserted through the posterior muscles (not shown) to allow access tothe damaged or herniated disk. Surgeons utilize special surgicalinstruments modified to work in such small openings such as curettes,osteotomes, reamers, probes, retractors, forceps, and the like to cutand remove part of the disk while monitoring their technique using amicroscope, a fluoroscope (real-time X-ray monitoring), and/or anendoscope (a miniature TV camera with associated viewing monitor). Whilethis technique is much less invasive than conventional open surgeries,due to their design the instruments presently available tend to extendthe length of time of the surgery and may cause possible damage to areasother than the herniated disk.

A spinal fusion is a procedure that involves fusing together two or morevertebrae in the spine using bone grafts and sometimes using metalfixation with screws, plates or metal rods. The removal of a significantamount of disk material or numerous surgeries often increases theinstability of the spine 120 thereby necessitating spinal fusionsurgery. The fusion procedure is often used to correct kyphosis orscoliosis, in addition to those patients who require spine stabilizationdue to vertebral damage from ruptured disks, fractures, osteomyelitis,osteoarthritis or tumors, and the like. In a fusion procedure, a damageddisk may be completely removed. Parts of a bone from another part of thebody, such as the pelvis, are harvested, and the bone parts or graftsare subsequently placed between the adjacent vertebrae 100 so that theadjacent vertebrae 100 grow together in a solid mass. In the fusionsurgery, which is presently performed as an open surgical technique, theposterior lamina 110 and the centers of the vertebral bodies 106 mayboth be cut. The surgery often involves consequential damage to theassociated posterior ligaments, muscles and joints in addition to theremoval of part or all of the lamina 110.

In general, small pieces of bone are placed into the space between thevertebrae to be fused, but sometimes larger pieces of bone are used toprovide immediate structural support. The source of the bone may be thepatient, (autologous or autograft bone) or a bone bank harvested fromother individuals, i.e. allograft bone. While autologous bone isgenerally considered better for promoting fusion between the vertebrae,it also necessitates extra surgery to remove bone from the patient'sbody. As with any surgery, risks can include bleeding, infection,adverse reactions to drugs, and difficulty under anesthesia.Additionally, the site of the bone graft harvest may cause pain inaddition to the pain the patient is already suffering due to thedifficulties associated with the vertebrae 100 or disk. Due to thenature of the conventional spinal fusion surgery, typically an opensurgery wherein muscles and ligaments are cut and bone is chiseled awayto allow access to the intervertebral space, recovery following fusionsurgery is generally longer than any other type of spinal surgery.Patients typically stay in the hospital for three or four days or moreand may require significantly greater time to return to normalactivities since the surgeon normally requires evidence of bone healing.The recovery time for a normal spinal fusion surgery is significant duenot only to the fact that normal movement cannot be allowed untildetectable bone growth has occurred between the bone grafts and theadjacent vertebrae 100, but the associated ligaments, muscles and thelocation where the bone grafts were harvested must also recover.Oftentimes portions of the spine 120 must be immobilized during therecovery period causing added discomfort and inconvenience to thepatient.

The concept of using a cage device for spinal fusion is not new. Severalfusion cages are disclosed in U.S. Pat. Nos. 4,961,740, 5,702,449,5,984,967, and 6,039,762, the subject matter of which is incorporatedherein by reference.

One prior art fusion cage device, disclosed in U.S. Pat. No. 4,961,740of Ray et al. (hereinafter “Ray”), is a large cylindrically shapedfusion cage that has a deep helical thread around the outer surface. Inorder to install the fusion cage of Ray, laminectomies must be performedon each side of the overlying lamina in order to provide access for thelarge cylindrically shaped fusion cage and if the disk space hasnarrowed as a result of degeneration, a scissors jack-type spreader orhydraulically inflated bladder is inserted on each side and opened toallow access to the disk space. A pilot cutter and pilot rod are used tocut female bone threads through the opposing vertebral endplates priorto threading the fusion basket into the now threaded interdiskal bore.Obviously the surgery is lengthy, highly intrusive and traumatic, and asnoted in the Ray specification takes several weeks for recovery.

Other prior art devices, disclosed in U.S. Pat. Nos. 5,702,449 and6,039,762 of McKay (hereinafter, “McKay”), are cylindrically shapedspinal implants with perforations or apertures located through theoutside walls. While the implants of McKay provide for a non-metal, bonegraft substitute, they still require open surgical techniques forimplantation due to their size and geometric shape.

Further, the concept of using an implant device for spinal support andstability is not new. Implants were used by Dr. Fernstrom in the 1960'sincluding stainless steel spherical ball bearings (see “SpineArthroplasty,” Spine Industry Analysis Series, Viscogliosi Bros., LLC,November 2001.).

What is needed, but not provided in the prior art, is a stand alonevertebral defect device that can be inserted into the intervertebralspace with minor open surgery in a procedure utilizing minimallyinvasive techniques. Further, there is a need for such a vertebraldefect device which can be used either to assist with fusion or can beused to maintain support and stability while preserving motion of theinvolved spine segment.

BRIEF SUMMARY OF THE INVENTION

Briefly stated the present invention comprises a vertebral defectdevice. The vertebral defect device includes a housing having a convexlytapered distal end, a convexly tapered proximal end, a top, a bottom, ananterior side, a posterior side and an outer surface having generallyrounded edges thereby facilitating insertion into an intervertebralspace between a pair of adjacent vertebrae. The length of the housing asmeasured from the distal end to the proximal end is greater than thewidth of the housing as measured between the anterior and posteriorsides and is greater than the height of the housing as measured betweenthe top and bottom.

The present invention further comprises a vertebral defect device. Thevertebral defect device includes a housing, an upper shelf and a lowershelf. The housing has a convexly tapered distal end, a convexly taperedproximal end, a top having a first opening to encourage vertebralfusion, a bottom having a second opening to encourage vertebral fusion,and an outer surface that is generally smooth thereby facilitatinginsertion into an intervertebral space between a pair of adjacentvertebrae. The upper shelf is disposed within the housing and isgenerally proximate to the first opening. The lower shelf is disposedwithin the housing and is generally proximate to the second opening.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofpreferred embodiments of the invention, will be better understood whenread in conjunction with the appended drawings. For the purpose ofillustrating the invention, there are shown in the drawings embodimentswhich are presently preferred. It should be understood, however, thatthe invention is not limited to the precise arrangements andinstrumentalities shown.

In the drawings:

FIG. 1 is a perspective view of a first preferred embodiment of avertebral defect device in accordance with the present invention;

FIG. 2 is a side elevational view of the vertebral defect device of FIG.1;

FIG. 3 is a front elevational view of the vertebral defect device ofFIG. 1;

FIG. 4 is a top plan view of the vertebral defect device of FIG. 1;

FIG. 5 is a side elevational view of a second preferred embodiment of avertebral defect device in accordance with present invention;

FIGS. 6A-6B are side elevational views of a third preferred embodimentof a vertebral defect device in accordance with present invention;

FIG. 7 is a side elevational view of the vertebral defect device of FIG.1 connected to a first preferred embodiment of an insertion tool inaccordance with present invention;

FIG. 8 is a side view of the vertebral defect device of FIG. 1 installedbetween lumbar vertebrae L^(III) and L^(IV);

FIG. 9 is a top sectional view of a human vertebra as is known in theart;

FIG. 10 is a side sectional view of a portion of a human spine as isknown in the art;

FIG. 11 is a side elevational view of a fourth preferred embodiment of avertebral defect device in accordance with the present invention;

FIG. 12 is a top plan view of the vertebral defect device of FIG. 11;

FIG. 13A is a side elevational view of a fifth preferred embodiment of avertebral defect device in accordance with the present invention;

FIG. 13B is a top plan view of the vertebral defect device of FIG. 13A;

FIG. 14A is a side elevational view of a second preferred embodiment ofan insertion tool for a vertebral defect device in accordance with thepresent invention;

FIG. 14B is a top plan view of the insertion tool of FIG. 14A;

FIG. 15A is a side elevational view of a third preferred embodiment ofan insertion tool for a vertebral defect device in accordance with thepresent invention;

FIG. 15B is a top plan view of the insertion tool of FIG. 15A;

FIG. 16A is a side elevational view of a fourth preferred embodiment ofan insertion tool for a vertebral defect device in accordance with thepresent invention; and

FIG. 16B is a top plan view of the insertion tool of FIG. 16A.

DETAILED DESCRIPTION OF THE INVENTION

Certain terminology is used in the following description for convenienceonly and is not limiting. The words “right”, “left”, “lower”, and“upper” designate directions in the drawing to which reference is made.The words “inwardly” and “outwardly” refer direction toward and awayfrom, respectively, the geometric center of the vertebral defect deviceand designated parts thereof. The terminology includes the words abovespecifically mentioned, derivatives thereof and words of similar import.Additionally, the word “a”, as used in the claims and in thecorresponding portions of the specification, means “at least one.”

The term “vertebral defect device” as used herein may be applicable to afusion cage device, a partial disk replacement device or a nuclearreplacement device without departing from the present invention, andshould be construed to broadly encompass any device for use incorrecting defects in the spine.

Referring to the drawings in detail, wherein like reference numeralsindicate like elements throughout, there is shown in FIG. 1 a vertebraldefect device 10 in accordance with a first preferred embodiment of thepresent invention. The vertebral defect device 10 has a housing, aconvexly-tapered distal end 10 a, a convexly-tapered proximal end 10 b,a lower wall 10 c, an upper wall 10 d, a first sidewall 10 e, and asecond sidewall 10 f (FIGS. 3, 4). An outer surface 12 is substantiallysmooth over the entire surface. The vertebral defect device 10 may betitanium, or any metal or alloy compatible with MRI scanners, syntheticor polymeric materials, composites, ceramic, a biocompatible polymericmaterial, any biologically absorbable material and the like withoutdeparting from the broad inventive scope of the present invention.

The vertebral defect device 10 is generally lens-shaped or ovoid-shapedwith rounded or contoured edges on all sides. In particular, theproximal end 10 b preferably is rounded but more bluntly-shaped than thedistal end 10 a which preferably is sloped into a bullet-shaped tip. Theproximal end 10 b is preferably generally ovoid-shaped. Thus, the distalend 10 a has a lesser average radius of curvature than the proximal end10 b. The lower wall 10 c and upper wall 10 d preferably are generallyconvex in order to cooperatively mate within the natural concavities ofadjacent vertebral bodies 100. Similarly, the first sidewall 10 e andsecond sidewall 10 f of the vertebral defect device 10 preferably aresimilarly convex for similar reasons and to facilitate installation ofthe vertebral defect device 10 into an intervertebral space 121. Theshape of the vertebral defect device 10 is ideally suited for insertionthrough a small opening, and therefore, the vertebral defect device 10is well suited for minimally invasive and/or outpatient procedures.

Distributed evenly about the surface 12 of the vertebral defect device10 are perforations or apertures 11. The apertures 11 are intended topromote rapid bone ingrowth while the vertebral defect device 10maintains a stiff support structure between the vertebrae 100 during thegrowth process. While in the presently preferred embodiment, theapertures 11 are shown as circular in shape, the apertures 11 could beany shape including ovals, squares, rectangles, triangles, diamonds,crosses, X-shapes, and the like without departing from the spirit andscope of the invention. But, there need not be apertures 11. Preferablyin the first preferred embodiment of the vertebral defect device, thelower wall 10 c defines a lower opening 16 a and the upper wall 10 d ofthe vertebral defect device 10 defines an upper opening 16 b at thepoint of vertebral contact to encourage successful fusion. The loweropening 16 a and the upper opening 16 b may be rectangular, circular,elliptical, or the like and may or may not be symmetrically-shaped. Theopenings 16 a, 16 b are preferably identically-shaped with respect toone another and are preferably symmetrically-shaped, but need not be.Further, the size of openings 16 a and 16 b may be varied to accommodatepatient variations.

The length of the vertebral defect device as measured from the distalend 10 a to the proximal end 10 b preferably is approximately 10-30 mm,depending on the particular intervertebral space 121 in which thevertebral defect device 10 is to be inserted. For example, theintervertebral space between lumbar vertebra L^(III) and lumbar vertebraL^(IV) for an average male would accommodate a vertebral defect device10 of a length between approximately 25-30 mm. But, the length of thevertebral defect device 10 could vary from the aforementioned rangewithout departing from the spirit of the invention.

The width of the vertebral defect device 10 as measured between thefirst sidewall 10 e and the second sidewall 10 f of the vertebral defectdevice 10 will vary from approximately 10 mm to 25 mm depending upon theparticular intervertebral space 121 in which the vertebral defect device10 is to be inserted. For example, the intervertebral space betweenvertebra L^(III) and vertebra L^(IV) in an average male wouldaccommodate a vertebral defect device 10 having a width of approximately15-20 mm. But, the width of the vertebral defect device 10 could varyfrom the aforementioned range without departing from the spirit of theinvention.

The height of the vertebral defect device 10 as measured between theupper wall 10 d and the lower wall 10 c of the vertebral defect device10 will vary from approximately 5 mm to 25 mm depending upon theparticular intervertebral space 121 in which the vertebral defect device10 is to be inserted. For example, the intervertebral space betweenvertebra L^(III) and vertebra L^(IV) in an average male wouldaccommodate a vertebral defect device 10 having a height ofapproximately 8-16 mm. But, the height of the vertebral defect device 10could vary from the aforementioned range without departing from thespirit of the invention.

The overall shape of the vertebral defect device 10 is designed forinsertion using minimally invasive techniques through a special portalor channel allowing a procedure to be implemented on an outpatientbasis. Further, the vertebral defect device 10 is a self centeringdevice because the shape of the vertebral defect device 10 willencourage it to settle within the natural concavities of adjacentvertebral bodies 100. As such, placement of the vertebral defect device10 is much faster than that of prior art devices, thereby effectivelyreducing the duration of a procedure and the associated risks therewith.The smooth contour and edges of the vertebral defect device 10 providefor a safe and easy entrance into the intervertebral space 121.

The convex, bullet-like shape of the distal end 10 a of the vertebraldefect device 10 will allow it to be driven into the intervertebralspace by merely temporarily distracting the vertebrae with minimalremoval of the vertebral rim or annulus (not shown clearly) at the pointof entry, thereby reducing the chance of dislodging the devicepost-surgery. Additionally, the self-centering feature of the vertebraldefect device 10 will allow rapid settling of the vertebral defectdevice 10 into adjacent bone to promote rapid bone ingrowth whileretention of most of the annulus and peripheral rim of the bodies(vertebrae) would provide good load sharing support to prevent excessivesubsidence, where subsidence results from the natural settling ofintervertebral matter into a softer central portion of the vertebralbodies 108.

FIG. 7 shows the vertebral defect device 10 of the first preferredembodiment with a first preferred embodiment of a specially designedinsertion tool 20. The insertion tool 20 is threaded into a socket 14 inthe proximal end of the vertebral defect device 10. The socket 14 isprovided with female threads 14 a which are configured to accept themale threads 20 a of the insertion tool 20. The insertion tool 20 may beformed of any substantially rigid material, but preferably is formed ofa material that is bio-compatible such as titanium, stainless steel,nickel, or of a bio-compatible alloy, composite, polymeric material orthe like. It should be noted that the material of construction of theinsertion tool could be any material without diverging from the broadscope of the present invention. It is also contemplated that theinsertion tool 20 and vertebral defect device 10 may be releasablycoupled by any of several releasable fastening mechanisms known to thoseskilled in the art.

FIGS. 14A-14B show a second preferred embodiment of an insertion tool200 for a vertebral defect device 10, 70, 80, 90, or 190 in accordancewith the present invention. The insertion tool 200 has an elongatehandle 202 and a grip 204. The grip 204 may be a suction cup or othersimilar gripping-type mechanism.

FIG. 8 shows a side view of the lumbar region 122 of a portion of ahuman spine 120. In particular, a vertebral defect device 10 inaccordance with the first preferred embodiment of the present inventionis shown installed between lumbar vertebra L^(III) and lumbar vertebraL^(IV). In this particular installation, the second sidewall 10 f of thevertebral defect device 10 is placed on the anterior side of theL^(III)-L^(IV) intervertebral space, the first sidewall 10 e of thevertebral defect device 10 is placed closest to the posterior side ofthe L^(III)-L^(IV) intervertebral space, the upper wall 10 d of thevertebral defect device 10 is adjacent to vertebra L^(III), and thelower wall 10 c of the vertebral defect device 10 is adjacent tovertebra L^(IV). In this example, the surgeon would have inserted thedistal end 10 a of the vertebral defect device 10 into the gap betweenthe L^(III)-L^(IV) vertebrae as depicted in FIG. 9 by a directionalarrow D. It is just as likely and possible for the surgeon to place thedistal end 10 a of the vertebral defect device 10 through the spacebetween the L^(III)-L^(IV) vertebrae in the direction of a directionalarrow C (FIG. 9) or from other directions.

FIG. 5 shows a side elevational view of a second preferred embodiment ofa vertebral defect device 70 in accordance with the present invention.The intervertebral defect device or vertebral defect device 70 has adistal end 70 a, a proximal end 70 b, a lower wall 70 c, an upper wall70 d, a first sidewall 70 e, and a second sidewall (not shown). An outersurface 72 differs from the first preferred embodiment only in that theouter surface 72 of the vertebral defect device 70 is a lattice-typestructure, instead of the body having a plurality of apertures 11, butthe outer surface 72 is also substantially smooth with rounded edges andcan be made from similar materials as described with reference to thefirst preferred embodiment. In an alternate embodiment of the secondpreferred embodiment of the vertebral defect device 70, the lower wall70 c defines a lower opening 76 a and the upper wall 70 d defines anupper opening 76 b at the point of vertebral contact to encouragesuccessful fusion.

FIGS. 6A-6B show a third preferred embodiment of a vertebral defectdevice 80 in accordance with the present invention. FIG. 6A shows thatthe vertebral defect device 80 has a distal end 80 a, a proximal end 80b, a lower wall 80 c, an upper wall 80 d, a first sidewall 80 e, and asecond sidewall (not shown). The vertebral defect device 80 further hasan outer surface 82, which in the present embodiment, is substantiallysmooth and free from apertures, openings, and the like. The presentlypreferred embodiment is ideally suited for use as a disk prosthesis ornuclear replacement-type device due to the lack of openings. It would beobvious to one skilled in the art to form the vertebral defect device 80out of a material that would not encourage adhesion or bone or tissuegrowth. Optionally, as shown in FIG. 6B, when the vertebral defectdevice 80 is applied as a fusion cage-type device, the lower wall 80 cdefines a lower opening 86 a and the upper wall 80 d defines an upperopening 86 b for intervertebral contact to encourage successful fusion.

FIGS. 11 and 12 show a fourth preferred embodiment of a vertebral defectdevice 90 in accordance with the present invention. The vertebral defectdevice 90 has a distal end 90 a, a proximal end 90 b, a lower wall 90 c,an upper wall 90 d, a first sidewall 90 e, and a second sidewall 90 f.The vertebral defect device 90 further has an outer surface 92, which inthe present embodiment, is substantially smooth and free from apertures,openings, and the like, but may have apertures without departing fromthe present invention. The lower wall 90 c defines a lower opening 96 aand the upper wall 90 d defines an upper opening 96 b for intervertebralcontact to encourage successful fusion. The vertebral defect device 90further includes a lower grating 98 a and an upper grating 98 b.Preferably, the gratings 98 a, 98 b are formed of a substantially rigidmesh that is coated with a bio-compatible ceramic to promote bonegrowth. The gratings 98 a, 98 b are located slightly below an outer edgedefined by the openings 96 a, 96 b in order to allow some or partialsubsidence of the vertebrae 100 partially into the vertebral defectdevice 90, but will prevent excessive subsidence. It has beencontemplated that in lieu of openings 96 a, 96 b, the gratings 98 a, 98b are merely recessed portions of the lower wall 90 c and upper wall 90d having perforations, apertures or slits which allow bone ingrowth.

FIGS. 13A and 13B show a fifth preferred embodiment of a vertebraldefect device 190 in accordance with the present invention. Thevertebral defect device 190 has a distal end 190 a, a proximal end 190b, a lower wall 190 c, an upper wall 190 d, a first sidewall 190 e, anda second sidewall 190 f. The vertebral defect device 190 further has anouter surface 192, which in the present embodiment, is substantiallysmooth and free from apertures, openings, and the like, but may haveapertures without departing from the present invention. The lower wall190 c defines a lower opening 196 a and the upper wall 190 d defines anupper opening 196 b for intervertebral contact to encourage successfulfusion. The vertebral defect device 190 further includes a lower grating198 a and an upper grating 198 b. Preferably, the gratings 198 a, 198 bare formed of a substantially rigid mesh that is coated with abio-compatible ceramic to promote bone growth. The gratings 198 a, 198 bare located slightly below an outer edge defined by the openings 196 a,196 b in order to allow some subsidence of the vertebrae 100 partiallyinto the vertebral defect device 190, but will prevent excessivesubsidence.

Further, the vertebral defect device 190 includes at least one upperarch 150 and at least one lower arch 152, but preferably the vertebraldefect device 190 includes three upper arches 150 and three lower arches152. The arches 150, 152 are generally disposed symmetrically along andabout a centerline of the longer axis of the vertebral defect device 190and are secured to the body of the vertebral defect device 190. Ofcourse the arches 150, 152 may be secured to the vertebral defect device190 by other means and may be disposed in other orientations withoutdeparting from the spirit of the present invention. Preferably, thearches 150, 152 protrude above the top and bottom 190 d, 190 c of thevertebral defect device 190, respectively. The arches 150, 152 areconfigured to settle into bone matter, and therefore, the arches 150,152 have sharpened edges 150 a, 152 a. The sharpened edges 150 a, 152 amay include serrations, pins, sharpened cones or a simple knife-likeedge, but need not be. Preferably, the sharpened edges 150 a, 152 a arepartially knife like proximate the ends of the arches and partiallycovered with sharpened cones 153. The arches 150, 152 are preferablyabout 0.5 mm to about 2.0 mm wide. The arches 150, 152 also serve tocenter the vertebral defect device 190 during placement and prevent thevertebral defect device from rolling or canting thereafter.

It should be obvious to one skilled in the art that arches 150, 152could be utilized in any of the embodiments of the vertebral defectdevices 10, 70, 80, 90, or 190, as described herein.

FIGS. 15A-15B show a third preferred embodiment of an insertion tool 220for a vertebral defect device 10 (70, 80, or 90) having upper and loweropenings 16 a, 16 b (76 a, 76 b, 86 a, 86 b, 96 a, 96 b). The insertiontool 220 has a first finger 222 configured to cooperatively engage theupper opening 16 a and a second finger 224 configured to cooperativelyengage the lower opening 16 b. The fingers 222, 224 have outer surfaceswhich are shaped to match the contoured shape of the vertebral defectdevice 10 to allow a smooth insertion of the vertebral defect device 10.The combination of the insertion tool 220 and the vertebral defectdevice 10 when the first and second fingers 222, 224 are engaged withthe ingrowth openings 16 a, 16 b, forms a combined structure havinggenerally rounded exposed surfaces. The fingers 222, 224 also preventforeign matter and debris from getting caught in the openings 16 a, 16 bduring insertion. Because the fingers 222, 224 grasp the vertebraldefect device 10 in a specific orientation defined by the upper andlower openings 16 a, 16 b, the insertion tool 220 provides the surgeonwith means to orient the vertebral defect device 10 correctly duringinsertion.

The insertion tool 220 further includes a driving member 226 that isconfigured to engage the body of the vertebral defect device 10. Thedriving member 226 is configured to be impacted such that duringinsertion a surgeon may tap or hammer the driving member 226 to push thevertebral defect device 10 through a small opening. Preferably, thefirst and second fingers 222, 224 are retractable relative to thedriving member 226. Thus, after the defect device 10 is inserted to adesired position, the first and second fingers 222, 224 are retractedwhile the driving member 226 holds the defect device 10 in place.Optionally, the vertebral defect device 10 may have grooves 166 (shownin phantom in FIG. 15B) extending from the upper and lower openings 16a, 16 b to facilitate the removal of the retractable fingers 222, 224.

FIGS. 16A-16B is a side elevational view of a fourth preferredembodiment of an insertion tool 230 for a vertebral defect device 190having upper and lower openings 196 a, 196 b and upper and lower arches150, 152. For example, the upper finger 232 has first and second prongs232 a, 232 b for straddling the upper arch 150 as best seen in FIG. 16B.The insertion tool 230 is similar to the insertion tool 220, but each ofthe retractable fingers 232 234 is forked to accommodate the arches 150,152. Preferably, the arches 150, 152 are just below the outer surface ofthe fingers 232, 234, so that the arches 150, 152 do not injure adjacenttissue during insertion. Furthermore, it would be obvious to one skilledin the art to utilize multiple prongs 232 a, 232 b in each of theretractable fingers 232, 234 in order to accommodate multiple arches150, 152.

The vertebral defect device 10 has a maximum height H and/or maximumwidth W, preferably in the range of 6 to 15 mm, at an axial locationintermediate the distal end 10 a and the proximal end 10 b. Thevertebral defect device 10 has a length L, preferably in the range of 10to 30 mm, along a longitudinal axis 42. An outer profile of thevertebral defect device 10 is characterized by a relatively gradualslope, such that the diameter (height and width) of the vertebral defectdevice 10 preferably changes no more than about 2 mm for every 1 mmchange in length. Preferably, the distal end 10 a, in particular, has aslope that changes by no more than about 2 mm for every 1 mm change inlength. The distal end 10 a is preferably relatively small, for example,less than 2.5 mm in diameter over the terminal 1 mm T of the distal end10 a along the longitudinal axis 42 or approximately 5-20% of themaximum height H and/or maximum width W of the vertebral defect device10. However, the distal end 10 a should not be so pointed such that itwould easily drive through or penetrate the opposite side of the annuluson the opposite side of the disk space. The taper and slope of thedistal end 10 a of the vertebral defect device 10 permit the vertebraldefect device 10 to be at least partially self-distracting. Generally,the vertebral defect device 10 is intended to be impacted into the diskspace while providing such distraction of the periphery of the vertebralbodies 100 to permit entry into nuclear center of the disk. Thevertebral defect device 10 may be dimensioned in accordance with therequirements of specific applications, and other dimensionalcharacteristics of the vertebral defect device 10 are included withinthe scope of this invention.

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. It is understood, therefore, that thisinvention is not limited to the particular embodiments disclosed, but itis intended to cover modifications within the spirit and scope of thepresent invention as defined by the appended claims.

1. A vertebral defect device comprising: a monolithically formed housinghaving a convexly tapered and generally bluntly rounded distal end, aconvexly tapered proximal end, a top, a bottom, an anterior side, aposterior side and an outer surface having generally rounded edgesthereby facilitating insertion into an intervertebral space between apair of adjacent vertebrae, a length of the housing as measured from thedistal end to the proximal end being greater than a maximum width of thehousing as measured between the anterior and posterior sides and beinggreater than a maximum height of the housing as measured between the topand bottom, the taper of the distal end diminishing more gradually thanthe taper of the proximal end and diminishing to the generally bluntlyrounded distal end, the taper of the distal end being configured toprovide distraction of adjacent vertebrae during insertion of thevertebral defect device, the distal end being less than 2.5 millimeters(mm) in diameter over a terminal 1 mm of the distal end, the maximumwidth of the housing as measured between the anterior and posteriorsides being different than the maximum height of the housing as measuredbetween the top and bottom; the distal end has a lesser average radiusof curvature than the proximal end; the top and bottom of the housingare at least partially convexly shaped enough to cooperatively mate withconcavities of adjacent vertebrae, the anterior and posterior sides areat least partially convexly shaped in order to allow installation of thevertebral defect device into the space defined by the concavities of theadjacent vertebrae, and wherein the vertebral defect device comprisesrounded edges on all of the exterior surfaces exposed during insertioninto an intervertebral space.
 2. A vertebral defect device comprising: amonolithically formed housing having a convexly tapered and generallybluntly rounded distal end, a convexly tapered proximal end, a top, abottom, an anterior side, a posterior side and an outer surface havinggenerally rounded edges thereby facilitating insertion into anintervertebral space between a pair of adjacent vertebrae, a length ofthe housing as measured from the distal end to the proximal end beinggreater than a maximum width of the housing as measured between theanterior and posterior sides and being greater than a maximum height ofthe housing as measured between the top and bottom, the taper of thedistal end diminishing more gradually than the taper of the proximal endand diminishing to the generally bluntly rounded distal end, the taperof the distal end being configured to provide distraction of adjacentvertebrae during insertion of the vertebral defect device, the distalend being about 5-20 percent of one of a maximum height of the housingas measured between the top and the bottom and the maximum width of thehousing; the maximum width of the housing as measured between theanterior and posterior sides being different than the maximum height ofthe housing as measured between the top and bottom; the distal end has alesser average radius of curvature than the proximal end; the top andbottom of the housing are at least partially convexly shaped enough tocooperatively mate with concavities of adjacent vertebrae, the anteriorand posterior sides are at least partially convexly shaped in order toallow installation of the vertebral defect device into the space definedby the concavities of the adjacent vertebrae, and wherein the vertebraldefect device comprises rounded edges on all of the exterior surfacesexposed during insertion into an intervertebral space.
 3. A vertebraldefect device comprising: a monolithically formed housing having aconvexly tapered and generally bluntly rounded distal end, a convexlytapered proximal end, a top, a bottom, an anterior side, a posteriorside and an outer surface having generally rounded edges therebyfacilitating insertion into an intervertebral space between a pair ofadjacent vertebrae, a length of the housing as measured from the distalend to the proximal end being greater than a maximum width of thehousing as measured between the anterior and posterior sides and beinggreater than a maximum height of the housing as measured between the topand bottom, the taper of the distal end diminishing more gradually thanthe taper of the proximal end and diminishing to the generally bluntlyrounded distal end, the taper of the distal end being configured toprovide distraction of adjacent vertebrae during insertion of thevertebral defect device, the distal end having a slope that changes nomore than about 2 millimeters (mm) for every 1 mm change in length; themaximum width of the housing as measured between the anterior andposterior sides being different than the maximum height of the housingas measured between the top and bottom; the distal end has a lesseraverage radius of curvature than the proximal end; the top and bottom ofthe housing are at least partially convexly shaped enough tocooperatively mate with concavities of adjacent vertebrae, the anteriorand posterior sides are at least partially convexly shaped in order toallow installation of the vertebral defect device into the space definedby the concavities of the adjacent vertebrae, and wherein the vertebraldefect device comprises rounded edges on all of the exterior surfacesexposed during insertion into an intervertebral space.